Electronic oscillator



June 21, 1938. L, MALTER 2,121,360

ELECTRONIC OSCILLATOR Filed March 28, 1936 2 Sheets-Sheet l June 21,1938. L. MALTER ET AL ELECTRONIC OSCILLATOR Filed March 28, 1936 2Sheets-Sheet 2 nnnnn Patented June 21, 1938 UNITED STATES PATENT OFFICEELECTRONIC OSCILLATOR Application March 28, 1936, Serial No. 71,360

5 Claims.

Our invention relates to electronic devices. More specifically, ourinvention deals with electronic tubes which depend upon the emission ofsecondary electrons.

We are aware of electronic devices in which a magnetic field, whoselines of force'are substantially parallel to the cathode, is employed.Such devices are called magnetrons, and require a heated cathode as anelectron emissive source. One of the Objects of the present invention isin means for establishing electronic oscillation without the uses of theheated cathode type of electron emitter.

Another object is to cause electronic oscillations to be establishedbetween a pair of concentric cylindrical electrodes one of which has anelectron emissive surface. A further object is to create a push-pulltype of electronic oscillator. A still further object is to restrict theelectronic movements to a region between the electrodes and therebyprevent excessive movement of electrons which will not contribute toefiicient operation.

Our invention may be best understood by rel.- erence to the accompanyingdrawings in which Figure I is a schematic diagram of one embodiment ofour invention,

Figure II is a schematic diagram of an electronic oscillator embodyingour invention and including electronic shields,

Figure III is a view illustrating a modification of Figure II,

Figure IV is a diagram of a push-pull oscillator embodying ourinvention,

Figure V is a view illustrating a modification of Figure IV, and

Figure VI is a diagrammatic view showing further modifications of myinvention.

In describing the several figures similar reference numerals will beused to indicate similar elements. In Figure I within an evacuatedenvelope I, a pair of concentrically arranged cylindrical electrodes 3,5 are suitably mounted by supporting wires 1, 9. The inner cylinder 5has its outer surface treated with caesium on silver oxide or any othersuitable material to make this electrode surface electron emissive. theouter or accelerating electrode preferably over-lap the inner orelectron emissive electrode.

The accelerating electrode is maintained at a positive potential withrespect to the emissive electrode by a polarizing battery H. A tunablecircuit I3 is serially connected between the electrodes as shown. Thetunable circuit is composed of'an inductor l5 and a variable capacitorThe ends of (Cl. 2508B) Figure I. battery 2| may be used as a source ofenergy.

The theory of the operation of our device is not entirely understood butit is believed that a small amount of residual gas within the envelopeor a photo-electric eifect of light falling on the electron emissivesurface may release electrons from the surface of the electron emissiveelement. These electrons start toward the positively chargedaccelerating anode at relatively high velocity. The magnetic fieldcauses these electrons to follow a curved path which extends out wardlyfrom the inner electrode toward the anode and back toward the cathode.The electron movement, or some similar effect, starts transient currentsflowing in the resonant circuit l3. These currents establish potentialswhich attract the electrons toward the secondary emissive surface atrelatively high velocities. The electrons moving at high velocities giveup their energy upon striking the electron emissive surface and therebyrelease a larger number of electrons. These electrons in turn starttoward the accelerating electrode which has again become relativelypositive and the cycle is repeated. At each repetition of the cycleincreasing numbers of electrons are emitted. The increasing electronemission and movement supports and sustains oscillations in the tunablecircuit I3.

The embodiment of our invention illustrated in Figure II is similar toFigure I with the addition of means to prevent the electrons from takingpaths outside of the juxtapositioned electrode surfaces. A pair of discs23, 25 having a diameter intermediate the diameter of the acceleratingand emissive electrodes are positioned adjacent the ends of the emissiveelectrode by supporting leads 21, 29. The disc shape electrodes areconnected to the battery 3|. The positive terminal of this battery 3| isconnected to the negative terminal of biasing battery II. The disc shapeelectrodes may be maintained at the same or different negativepotentials. The negatively polarized discs will maintain the electronfield within the proper boundaries for maximum efflciency. These discsare preferably made of a material which does not impair the magneticfield.

In Figure III a modification of Figure II has been illustrated in whicha pair of mica discs 33, are substituted for the disc electrodes 23, 25.

The mica discs are self-biasing; i. e., electrons strike the disc andcharge it negatively. The negatively charged discs repel electrons whichmight otherwise follow paths beyond the adjacent surface or theaccelerating and emissive electrodes.

In Figure IV, a schematic representation illustrates an embodiment ofour invention applied to a push-pull oscillator. Within an evacuatedenvelope H a cylindrical accelerating anode 49 is supported by suitablewires 45. A pair of cylindrical electrodes 41, 49 are concentricallymounted within the accelerating anode by supporting wires SI, 53. Theouter surfaces of these electrodes 41, 49 are treated to render themhighly secondary emissive. The leads BI, 53 from the electrodes 41, 49are respectively connected to the opposite terminals of a tunablecircuit which is composed of an inductor 51 and a capacitor. Apolarizing battery 0| is connected between the accelerating anode 43 andthe mid-point 63 on the inductor 51. The positvie terminal of -thebattery is connected to the anode. The magnetic field has beenrepresented as a magnetic core 01 which is energized by current frombattery 09 flowing in the solenoid winding II. It should be understoodthat a solenoid type winding may be used in place of the electromagnetshown. Disc shape electrodes 23, 25 may be placed adjacent the ends of.the cylindrical electrode 41. Likewise disc shape electrodes 23, 25 maybe located adjacent the ends of the cylindrical electrode 49. The discshape electrodes 23, 25 are biased negatively by suitable connections tonegative termirials of a battery 3|. The positive terminal of thebiasingbattery 3| is connected to the positive terminal of thepolarizing battery BI.

In Figure V the essential elements are similar to the elements of FigureIV. In the instant arrangement the electrode arrangement is reversed.The inner electrode 8I is made with an electron emissive surface, andthe pair of outer electrodes 83, 05 act as accelerating anodes. Theaccelerating anodes 83, 85 are connected to the terminals of the tunedcircuit 55. The inner electrode 8| is connected to the negative terminalof the battery GI whose positive is connected to the mid-point 63 ofinductor 51, The magnetic field may be due to an electromagnet,permanent magnet or solenoid.

The theory of operation of each of the pushpull oscillators isessentially the same as the single electronic oscillators describedabove. Inasmuch as push-pull operation is well known to those skilled inthe art, a detailed description is unnecessary. It should beunderstoodlthat various features of the several embodiments of ourinvention may be combined. By way of example, he accelerating andemissive electrodes of Figures I, II or III may be interchanged,accompanied, of course, by a proper phasing of the biasing battery.Likewise, the disc or shielding electrodes of Figures II or III may beemployed with the arrangement shown in Figure V, as for exampleillustrated in Figure VI.

Referring to Figure VI, within an envelope I00 are arranged a pair ofinner cylindrical electrodes IOI, I03. The outer surfaces of theseelectrodes are treated to make them secondarily emissive. Adjacent theends of the inner electrodes are equivalent to the operation of thecircuits previously described.

We claim as our invention:

1. An electron oscillator comprising an evacuated envelope, a hollowcylindrical electrode mounted within said envelope, a pair of.cylindrical electrodes of substantially the same diameter spaced apartand coaxially mounted within the first mentioned electrode, said pair ofelectrodes having surfaces adapted to emit secondary electrons uponimpact of primary electrons, a tuned circuit, connections from one ofthe terminals of said tuned circuit to one of said pair of electrodesand from the other terminal to the other electrode of said pair, asource of polarizing potential connected beween the outer electrode ofsaid concentrically mounted electrodes and said tuned circuit, and amagnetic field whose lines of force are substantially coaxial withrespect to said concentrically mounted cylinders.

2. An electron oscillator comprising an evacuated envelope, acylindrical electrode mounted within said envelope, said electrodehaving suriace adapted to emit electrons upon electron impact, a pair ofhollow accelerating anodes spaced apart and concentrically mounted withrespect to said first mentioned electrode, a tunable circuit,connections from said tunable circuit to said pairs of electrodes, asource of biasing potential connected between said first-mentionedelectrode and said tuned circuit, and a. magnetic field whose lines offorce are substantially coaxially arranged with respect to saidconcentrically mounted electrodes.

3. A device of the character of claim 1 including means for maintainingthe electronic movements within the juxtapositioned electrode surfaces.

4. A device of the character of claim 2 including means for maintainingthe electronic movements within the juxta-positioned electrode surfaces.

5. An electron oscillator comprising an evacuated envelope, acylindrical electrode mounted within said envelope, a pair of electrodesspaced apart and concentrically mounted with respect to said firstmentioned electrode, at least one of said pair of electrodes having asurface of secondarily emissive electron material, a tunable circuit,pushpull circuit connections between said tunable circuit and saidelectrodes, means for polarizing said first mentioned cylindricalelectrode positively with respect to said emissive electrode orelectrodes, and means for establishing a magnetic field whose lines offorce are substantially coaxial with respect to said cylindricalelectrode.

LOUIS MALTER. JAN A. RAJCHMAN. ROBERT RHEA GOODRICH, 2ND.

